There is a way to adjust the computer to be more accurate on your mpg. I read about it on an F150 Forum.
Here ya go:
Take your hand calculated MPG and divide it by the computer display MPG....then multiply by 1000. This new number is what you will change the AFE Bias to.
Example: 18.3/19.6 = .9337xxxx. Multiply by 1000 = 934 (rounded up) as the number to use.
For Lariat and up 8 inch meter Display:
Engine off.
1. Press and hold OK Button on the left side of the steering wheel and don't release it until the end.
2. Press push start Button only (Not Brake Pedal) to turn to Accessory Mode.
3. Once Message*accessory Mode appears.... press the Brake Pedal and turn the Engine on.
4. Engineering Test Mode appears instantly. Release OK button.
5. Scroll to AFE Bias and push OK to change it to the number you calculated. Note, it takes quite a few clicks to get to AFE Bias.
6. Once done, turn off truck and it will update your mpg, including your Trip 1 and Trip 2. You'll see it has changed the next time you start the truck.
Note....quite a few of us have been successful just holding down the OK button, starting the truck, then releasing the OK button once Engineering Mode pops up.
For 4.2 inch meter Display:
Engine off.
Press and hold OK Button on the left side of the steering Wheel.
Continue holding OK button and start the engine...don't let go of OK button until "Engineering Test Mode" appears.
Go through the menu pressing and releasing OK Button until you reach "AFE Bias 1000" appears.
Press and release Down. Using Left and Right change 1000 to the Number You calculated. Press OK.
To leave Engineering Mode after you are done, just turn the engine off.